Propulsion of ships and the like by means of rotors comprising radial vanes, where the rotors are oriented transverse to a longitudinal axis of the ship, has long been a recognized way of applying propulsive power to water.
In the last century or so, it has become common practise to propel ships and the like by means of one or more propellers rotating about an axis of rotation co oriented with a longitudinal axis of the ship. The one or more propellers typically are driven by power plants burning fuel oil.
Power plants of ships are assigned to comply with various regulations limiting the power plants levels of emissions.
Recent tightening of the regulations relating to ships' levels of emission in coastal regions has forced ship owners and operators to seek alternative ways of powering their ships as levels of emission, when operating on heavy fuel oil, exceed the permissible levels as set forth by the regulations.
One widely applied solution has been to operate the ships, in coastal regions, on more environmental friendly oils such as light gas oil; however, with the latest tightening of the regulations, even when operating on light gas oil, the levels of emission violates the regulations.
Owners and operators therefore are looking for alternative ways of propelling their ships, particular in coastal regions.